Iran is installing more centrifuges in an underground plant but does not yet appear to be using them to expand higher-grade uranium enrichment that could take it closer to producing atom bomb material, Western diplomats say.
They say Iran's production of uranium refined to a fissile concentration of 20 percent, which it started two years ago, seems to have remained steady in recent months after a major escalation of the work in late 2011 and early this year.
Progress in Iran's controversial nuclear program is closely watched by the West and Israel as it could determine the time the Islamic Republic would need to build nuclear bombs, should it decide to do so.
Getting Iran to stop the higher-level enrichment is expected to be a priority for world powers when they meet with Iran in Baghdad next week in an attempt to start resolving the decade-old dispute over Tehran's atomic ambitions.
"It is still going strong. I hear it is unchanged," one diplomat accredited to the UN nuclear watchdog, which regularly inspects Iran's declared atomic sites, said about the country's most sensitive nuclear activity.
"But with installation work going on, at some point there will be an increase."
Tehran took a big step towards the capability of making nuclear weapons material after a previous attempt at diplomacy failed when, spurning UN demands to halt all enrichment, it instead ramped up uranium processing to 20 percent purity.
That provoked the West to impose crushing sanctions on its banks and oil exports.
A UN nuclear report published in February showed Iran trebling output of 20 percent uranium since late 2011 after starting up production at the Fordow underground plant near the Shi'ite Muslim holy city of Qom and later increasing it.

JPost.com